// Security by tool
Security for apps built with v0
Quick answer
v0 generates very good UI and code, but the risk is not in the isolated component, it is in how you integrate: a dangerouslySetInnerHTML pasted without sanitizing, an API key hardcoded in a client component, a form handler that trusts user input, and the deployed app shipping without CSP. v0 does not solve any of these for you; they show up at the seam between what was generated and your backend.
If you assembled the product by pasting v0 pieces, the right review looks at the boundary: where input enters, where secrets live, and what the server action actually validates before writing to the database.
What tends to slip through in v0
The v0 pattern is UI-first with Next server actions and route handlers. The generated code works, but v0 writes functional flows, not secure flows, without explicit instruction. The points that break most:
| Hole | Why it happens | Impact |
|---|---|---|
| dangerouslySetInnerHTML | Pasted snippet renders HTML without sanitizing | XSS via user content |
| Key in a client component | Secret hardcoded in code that runs in the browser | Credential exposed in the bundle |
| Server action without authz | Functional action that does not check the data owner | IDOR / unauthorized writes |
| No CSP on deploy | App published without Content-Security-Policy | Larger surface for injection |
How RET reviews a v0 app
RET tests the seam: every server action and route handler is checked for who can call it, with what validation, and whether it verifies the resource owner. It hunts for dangerouslySetInnerHTML without sanitization, secrets in client components and missing CSP. Findings ship with reproduction and priority.
To run it yourself, the Promptbook covers these points with direct prompts. Serious signals go to Risk Review.
- Audit of each server action: who calls it, what it validates, does it check the owner?
- Search for dangerouslySetInnerHTML and secrets in client components.
- CSP and header check on the deployed app.
You may already be exposed if
Signals that call for a review in a v0 app:
- You use dangerouslySetInnerHTML with content that comes from the user.
- Some API key sits in a file that runs on the client.
- Your server actions write to the database without checking the data owner.
- The app was published without a Content-Security-Policy.
Frequently asked questions
Is v0 code insecure?
Not on its own. v0 generates functional, clean code; the risk shows up in integration, when a snippet with dangerouslySetInnerHTML, a key in the client, or a server action with no owner check enters your app without review. It is the seam that needs eyes.
Is a Next server action secure by default?
It runs on the server, which helps, but it does not validate authz on its own. An action that writes to the database needs to check that the logged-in user owns that resource, otherwise it becomes IDOR. v0 writes the functional action; the owner check is yours.
Do I really need CSP?
CSP greatly reduces the damage of an XSS, which is exactly the risk of pasting dangerouslySetInnerHTML. Shipping without CSP is not an isolated bug, but it amplifies any injection. Worth configuring before real users arrive.
Who runs the review at RET?
Gabriel Lima Ferreira, founder and lead pentester, with authorization and a tight scope.